When a suitable amount of toe angle is given to the outer rear wheel of a vehicle making a turn so as to tilt the outer rear wheel inwardly with respect to the turning circle of the vehicle, because the slip angle required for the outer rear wheel can be achieved while involving a relatively small vehicle body slip angle, a relatively brisk rise in the cornering force can be achieved as the front wheels are steered. This is desirable as it improves the handling of the vehicle. In particular, it is beneficial to cause the toe angle of the outer rear wheel, which supports a larger part of the vertical load, to change so as to turn inward with respect to the turning circle when subjected to a side force.
To achieve such a tendency, which is called as a side-force steer-in property, a suitable amount of toe compliance is required for each rear wheel suspension system. On the other hand, for the vehicle to be able to recover itself briskly from a turning maneuver and to improve the stability of the vehicle when traveling straight ahead, each wheel suspension system is required to have a high camber rigidity. Therefore, the rear wheel suspension system is required to have two conflicting properties, rigidity and compliance. From a practical view point, it is desirable for the rear wheel suspension system to have as high a rigidity as possible to allow a desired handling of the vehicle to be achieved.